1. Field of the Invention
The present invention relates to a light device, a communication unit and a positional information management system.
2. Description of the Related Art
Various positional information management systems have been proposed to determine and manage the position of a wireless terminal, or a person or a thing which has a wireless terminal, in such a facility or the like in which it is difficult to accurately carry out positioning using GPS or the like.
In such a positional information management system, a plurality of transmitters for transmitting positional information to the wireless terminals are installed on the ceiling of a room or the like for example. However, for this purpose, new power supply installation work is needed for supplying the power to the transmitters, and thus, the introduction cost may be increased.
International Patent Publication No. 2005/086375 discloses a system in which the position of the wireless terminal is determined as a result of the wireless terminal receiving unique information from a light device and transmitting the unique information to a server. According to the system of International Patent Publication No. 2005/086375, communication with the wireless terminal is made available using the power supplied to the light device as a result of providing the light device with a function of transmitting the unique information to the wireless terminal. Thus, it is not necessary to carry out new power supply installation work at a time of introducing the system.
However, power consumption in the wireless terminal may be increased depending on the communication system employed between the wireless terminal and the server according to the system of International Patent Publication No. 2005/086375. Further, the server needs to search for the position associated with the unique information in order to determine the position of the wireless terminal, and the calculation cost may be thus increased.